The present invention relates generally to inspection of semiconductor devices for the purpose of identifying defects thereon. Additionally, it relates to techniques for classifying defects found on integrated circuit devices.
Semiconductor defects may include structural flaws, residual process material and other surface contamination which occur during the production of semiconductor wafers. Defects are typically detected by a class of instruments called inspection tools. Such instruments automatically scan wafer surfaces and detect, and record the location of optical anomalies using a variety of techniques. This information, or “defect map,” is stored in a computer file and sent to a defect review station.
Using the defect map to locate each defect, a human operator observes each defect under a microscope and classifies each defect according to class (e.g., particle, pit, scratch, or contaminant). Information gained from this process is used to correct the source of defects, and thereby improve the efficiency and yield of the semiconductor production process. Problems with this classification method include the technician's subjectivity in identifying the defect class, and the fatigue associated with the highly repetitive task of observing and classifying these defects.
One type of inspection or review tools that may be used to classify a defect are electron beam (ebeam) induced X-ray tools. An ebeam induced X-ray tool directs an e-beam towards the defect and X-rays are emitted from the defect as well as any surrounding material in response to the e-beam. The X-rays may then be analyzed to determine a composition of the defect. Typically, the X-rays are compared to X-rays emitted from a substrate having no defect. The X-ray spectra for the substrate without a defect is subtracted from the substrate having the defect to obtain the X-ray spectra for the defect. Although one can easily determine a composition of a defect when the substrate is formed from a single material, such as silicon, it becomes rather difficult to identify a defect's composition when the substrate is complex and formed from several different structures and materials. This technique would require obtaining reference X-ray spectra from multiple substrate specimens having no defects to thereafter compare to defects on such complex substrates. Additionally, one would have to determine the substrate type for each type of defect and then use the appropriate reference X-ray spectra to determine the defect's composition.
Accordingly, there is a need for improved mechanisms for classifying defects using an e-beam induced X-ray inspection or review system or the like.